Treatment of metallic surfaces



252. COMPOSITIONS,

Patented Dec. 15,

UNITED STATES Exam PATENT OFFICE WILLIAM 1?. TER HORST, OF PAGKANACK LAKE, WAYNE, NEW JERSEY, ASSIGNOR TO THE NAUGATUC'K CHEMICAL COMPANY, OF NAUGATUGK, CONNECTICUT, A CORPO- RATION OF CONNECTICUT TREATMENT OF METALLIC SURFACES No Drawing.

This invention relates to the treatment of metallic surfaces where the surface is subjected to the action of liquids of an acid nature. More particularly, the invention relates to the prevention of excessive pitting, embrittlement, and undesirable dissolution of metal during contact with an acidic liquid. The invention also provides a pickling bath containing a new class of inhibitors; particularly for the pickling of such as iron and steel.

LLh gbee f l lidthat..c,ondensation prod: ucts aleelarcleaaaiemieania,a nediee to a ickiin'gbath greatly fr fird the attack of the acitl'on such as iron and steel without materially influencing the attack of the acid material on scale or rust. Typical of these inhibitors are such as the condensation products of heptaldehyde and ammonia.

Accordingly the invention broadly comprises incorporating in a usual pickling bath,which may or may not contain any of the known inhibitors,one or more of the aldehyde-ammonia condensation products, preferably those'in which heptaldehyde is used as a reactant. When such as iron or steel is placed and kept therein for a suitable length of time at a suitable temperature,

the metal is freed from scale and rust and after removal presents a smooth surface which can then be coated in the customary way with any protective or ornamental coating.

The following is illustrative of the invention but is not to be considered as limiting thereof.

Indicative of the preparation of the inhibitors the following example is given:

E azampZe.Heptaldehyde-ammonia condensation product. This material is made by heating equimolecular quantities of'heptaldehyde and ammonia in an autoclave at 130 C. during several hours. After the reaction has been completed the material may be steam distilled, and dried under vacuum.

Also the heptaldehyde and ammonia may be allowed to react at room temperature, for example, 20 grams of heptaldephde were slowly added to 37 grams of 28%% aqueous ammonia. The mixture is allowed to stand dur- Application filed May 9, 1930, Serial No. 451,197. Renewed October 28, 1931.

ing 16 hours at room temperature after which used as such or mixed with other chemicals such as frothing agents, or diluents such as spindle oil, or both.

Further illustrative examples of the invention are hereby given below:

Example 1.Opcn hearth steel is used in all tests. Pieces three inches square are pickled during one hour in 10% sulphuric acid solution at a temperature of to C. The loss of weight was determined and calculated on a percentage basis. In the following table are given the results in the absence and in the presence of heptaldehyde-ammonia. The relative losses in weight indicate the extent to which the metal is attacked in the bath.

Table I Amount of acid used, 125 cc. Amount of inhibitor, 67 mg.

Weight of steel mgrams Loss in Percentgrams age loss Before After pickling pickling Blank 31.4350 29.9350 1.5000 4.76 I'Heptaldehyde ammonia condensation product 31.7150 31.650 .0200 .06

Another way of determining the efliciency of an inhibitor is by the hydrogen measurement method which measures the amount of hydrogen gas which is evolved during pickling. This method is carried out as follows:

Example 2.Open hearth steel strips 1x% are put in a gas buret; 360 cc. 10%

sulphuric acid are added and part of the acid is sucked into the buret until the same is full. This experiment is called the blank. Another experiment is run in a similar way, except that, to the sulphuric acid is added 92 mg. of heptaldehyde ammonia condensation product. The amount of hydrogen evolved inn;

is measured hourly. Results are given in Table II.

Table II Cubic centimeters of hydrogen evolved 1' Heptaldehyde am- Blank monia condensation product 1 hour 4. 5 0. 6 2 hours 9. 3 1. 9 3 hours 19.6 3. 0 4 hours 29. 7 4. 9 5 hours 38. O 5. 9

After 5 hours pickling the blank had given off 38 cc. of hydrogen whereas the sulphuric acid containing 92 mg. of heptaldehyde ammonia condensation product had caused the evolution of only 5.9 cc. of hydrogen.

Instead of using heptaldehyde-ammonia, the reaction products of ammonia with other aliphatic aldehydes may be used. Instead of using single acids a mixture of single acids may be used, for example a mixture of hydrochloric and sulphuric acids, in the pick- I ling operation.

With the detailed description given above, it will be clear various changes may be made without departing from the principle of the invention, for instance the bath need not necessarily be what is known as a pickling bath but may be used in connection with any condition where metal would be attacked by acid liquids, and the invention is not to be limited except as indicated in the appended claims.

Having thus described my invention, what l claim and desire to protect by Letters Patent 1s:

1. A process of protecting a metal surface such as iron, steel or the like against undesirable dissolution by acids which comprises treating the metal with an acid solution containing the reaction product of an aliphatic aldehyde and ammonia.

2. A process of protecting a metal surface such as iron, steel or the like against undesirable dissolution by acids which comprises treating the metal with an acid solution containing the reaction product of heptaldehyde and ammonia.

3. A pickling bath for iron and steel products comprising a pickling acid and the reaction product of an aliphatic aldehyde and ammonia.

4. A pickling bath for iron and steel products comprising a pickling acid and the reaction product of heptaldehyde and ammonia.

Signed at New York, county of New York, State of New York this 8th day of May, 1930.

WILtIAM P. TEE HORST. 

